All You Need to Know About HVAC Diffusers

HVAC diffusers are components that control heating and cooling airflow into each room. Diffusers are mounted at the point where an HVAC duct enters a room through the wall or ceiling. However, they are far more than just a decorative device to cover the gaping opening that delivers conditioned air.

The HVAC system in an average-size residence distributes about 2,000 CFM (cubic feet per minute) of heated or cooled air throughout the rooms in the house.  HVAC diffusers regulate the direction and volume of airflow in order to disperse air evenly and ensure consistent temperature control in rooms of differing size and shape. Diffusers also help to dampen the noise of moving air as it flows into the room.

Different Shapes For Different Rooms

A basic ceiling HVAC diffuser may be a non-adjustable round shape to evenly spread air in a 360-degree pattern for uniform cooling or heating throughout the room. Another type is a square or rectangular shape mounted high on a wall with manually adjustable slats which control both vertical and lateral direction of airflow to fit the particular room shape and dimensions.

Diffusers Vs. Grills

Diffusers are always installed over supply ducts and specifically designed to direct and control conditioned airflow. Most return air ducts, conversely, are covered by a simple grill that mainly functions to keep foreign objects out of the duct.

Diffuser Specifications

An HVAC professional utilizes several  parameters when choosing the right diffuser to maximize system effectiveness:

  • “Throw” refers to the horizontal distance the flow of air travels from the diffuser into the room.
  • “Drop” refers to downward velocity of air leaving the diffuser opening. Excessive drop creates the sensation of a cold or hot draft in a room while a lesser amount of drop is less noticeable and generally preferable.
  • “Spread” expresses how widely air is dispersed inside a room. A wider spread generally reduces the amount of drop and also eliminates cold or hot spots inside a room.

More questions about HVAC diffusers? Paitson Bros. has the answers. Since 1922, we’ve been your Terre Haute source for reliable HVAC information.

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    Jeff Paitson Jeff Paitson is a third generation business owner who continues to run the business with the same values that have been passed down from previous generations since 1922.

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